The Phantom Pain is Metal Gear Solid 5, developed by Kojima Productions

So, guess Moby Dick Studio wasn't real after all. In a new trailer shown at GDC 2013, Hideo Kojima (wrapped in bandages) revealed a new trailer for The Phantom PainMetal Gear Solid 5--as many suspected.
Hideo Kojima revealed that Metal Gear Solid 5 is the combination of bothMetal Gear Solid: Ground Zeroes and The Phantom Pain. In MGS5, Snake wakes up from a nine years-long coma, and must regain his strength to escape the hospital found in TPP's VGA debut. Kojima pointed out that after escaping the hospital, players will have access to the open-world gameplay promised by Ground Zeroes.
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The real-time demo of the FOX Engine showing off MGS5 gameplay was presented on PC, with an Xbox 360 controller. Update: According to a Konami press release, Metal Gear Solid 5: The Phantom Pain is still only announced for PS3 and Xbox 360 only.

Kojima Productions talks up the FOX Engine at GDC

Joining Kojima was Hideki Sasaki, CG art director, Junji Tago, technical director, and Masayuki Suzuki, lighting artist. They proceeded to talk up the capabilities of the engine, showing off a number of real-time demos running on PC.
One of the most impressive tricks employed by the KP team was "PhotoScan," which gets incredibly detailed 3D scans from photographs. A clay model of an actor's head was created, and then scanned into the FOX Engine with a level of recreation that earned applause from the audience--especially when revealing the underlying wireframe model.

Kojima Productions talks up the FOX Engine at GDC

Another tool used by the Kojima team was "Marvelous Designer 2," which enables realistic cloth to be rendered. Essentially, it allows modelers have a virtual Ken doll, easily stitching together pieces of cloth onto a mannequin and adjusting by hand. The engine can make realistic wrinkles in real-time, before converting to a high-poly output when finished.
While the FOX Engine's incredible lighting adds to the believability of the visuals, it's the extensive attention to the engine's virtual camera that adds a cinematic touch to MGS5. Camera parameters are based on real-world values, with the engine's digital lens able to adjust exposure, focal length, shutter speed, aperture.
Concluding the talk, Kojima Productions announced an official Los Angeles-based studio. The logo for Kojima Productions Los Angeles wants to "become the top creative development studio in the world," with a vision towards creating "the highest quality interactive entertainment which brings deep emotional experience."